NC State Extension Publications

Symptoms

Early symptoms include small, yellow flecks that develop on the leaves and stems. The flecks expand over time into raised pustules, yellow or orange in color, that rupture to release powdery masses of spores. Infected plants become yellow and are more susceptible to environmental stress. Heavily infected areas become thin and exhibit clouds of orange dust (rust spores) when the foliage is disturbed. The rust pustules on infected leaves turn black during the fall in preparation for overwintering.

Development Factors

Rust fungi survive the winter in living plant tissue from which new spores are produced in the spring. Spores produced in the spring, summer, and fall are spread by the wind, germinate on the leaves, and infect new tissue. Extended periods of leaf wetness are required for the spores to germinate and for the disease to develop rapidly.

Rust diseases are most severe in turf that is growing slowly due to adverse weather conditions or inadequate management. Low light intensity, inadequate fertilization, drought stress, and infrequent mowing encourage rust development.

Cultural Control

Plant rust-resistant turfgrass varieties whenever possible to reduce injury from this disease. Select cultivars based on regional trials and university recommendations. When planting cool-season turfs, use blends and mixtures of multiple species and/or varieties whenever possible. Plant shade tolerant grasses and raise mowing heights in heavily shaded areas.

Prune trees and remove unwanted undergrowth to improve air movement and reduce prolonged leaf wetness. Mow the turf on a regular basis, removing no more than 1/3 of the foliage in one mowing. Collect and dispose of clippings taken from infected areas to slow the spread of rust.

Fertilize to meet the nutritional needs of the turf. Submit a soil sample for analysis on a regular basis and apply recommended amounts of phosphorus, potassium, and lime. Apply nitrogen based on university recommendations.

Use the Turf Irrigation Management System available on TurfFiles to schedule irrigation based on weather conditions and turf needs. Water deeply but infrequently to encourage deep rooting and reduce drought stress and extended periods of leaf wetness. Avoid watering the turf before sunset or after sunrise.

Chemical Control

Fungicides can be used on a preventative or curative basis for rust control. Susceptible turfs should be monitored regularly for rust development during periods of cool and cloudy weather.


Fungicide and Formulation1 Amount of Formulation2 Application Interval3 Efficacy Rating Resistance Risk
azoxystrobin (Heritage, Strobe)
(Heritage TL)
(Heritage G)
0.2 to 0.4
1 to 2
2 to 4 lbs
14 to 28
14 to 28
14 to 28
++++ High
azoxystrobin + acibenzolar-S-methyl (Heritage Action)* 0.2 to 0.4 14 to 28 ++++ High
azoxystrobin + chlorothalonil (Renown)* 2.5 to 4.5 14 to 21 ++++ High
azoxystrobin + difenoconazole (Briskway)* 0.5 to 0.725 14 to 28 ++++ High
azoxystrobin + propiconazole (Headway)
ME
G
1.5 to 3
2 to 4 lbs
14 to 28
14 to 28
++++ High
azoxystrobin + tebuconazole (Strobe T)* 0.75 to 1.5 14 to 21 ++++ High
chlorothalonil
Daconil Ultrex)*
(Daconil Weather Stik, Legend)*
(Daconil Zn)*
(Chlorothalonil 500ZN)*

(Chlorothalonil 720SFT)*

(Chlorothalonil)*


3.7 to 5
4.0 to 5.5
6 to 8
3 to 5
7.9
2.12 to 3.5
5.5
3.2


14
14
14
7 to 14
14
7 to 10
14
7 to 14
+++ Low
chlorothalonil + acibenzolar-S-methyl (Daconil Action) * 4 to 5.4 14 +++ Low
chlorothalonil + fluoxastrobin (Fame C)* 3 to 5.9 14 to 28 ++++ Medium
chlorothalonil + propiconazole
(Concert)*
3 to 5.5
4.5 to 8.5
7 to 14
14 to 28
++++ Medium
chlorothalonil + propiconazole + fludioxonil (Instrata)* 2.75 to 6 14 to 28 ++++ Medium
chlorothalonil + thiophanate-methyl (Spectro)*
(TM/C)*
3.72 to 5.76
3 to 8
14
14 to 21
+++ Medium
fluoxastrobin (Fame) 0.18 to 0.36 14 to 28 ++++ High
mancozeb(Fore)*(Dithane)* 44 7 to 1410 ++ Low
metconazole (Tourney) 0.37 14 ++++ Medium
myclobutanil (Eagle, Myclobutanil) 1.2 14 to 28 ++++ Medium
propiconazole (Banner Maxx, Propiconazole) 1 to 2 14 to 28 ++++ Medium
pyraclostrobin (Insignia) WG
SC
0.5 to 0.9
0.4 to 0.7
14 to 28
14 to 28
++++ High
pyraclostrobin + boscalid (Honor)* 0.55 to 1.1 14 to 28 ++++ High
pyraclostrobin + fluxapyroxad (Lexicon Intrinsic) 0.34 to 0.47 14 to 28 ++++ High
tebuconazole (Torque)*
(Mirage)*
(Tebuconazole)*
0.6 to 1.1
1 to 2
0.6
refer to label
14 to 28
28
++++ Medium
triadimefon (Bayleton) 0.5 to 1 15 to 30 ++++ Medium
trifloxystrobin (Compass) 0.1 to 0.15
0.2 to 0.25
14
21
++ High
trifloxystrobin + triadimefon (Armada)
(Tartan)*
0.6 to 1.2
1 to 2
14 to 28
14 to 28
++++ High
triticonazole (Trinity)
(Triton)
0.5 to 1
0.15 to 0.225
14 to 28
14 to 28
++++ Medium
triticonazole + chlorothalonil (Reserve)* 3.2 to 4.5 14 to 28 ++++ Medium
1 Other trade names with the same active ingredients are labeled for use on turfgrasses and can be used according to label directions.
2 Apply fungicides in 2 to 5 gallons of water per 1,000 square feet according to label directions. Use lower rates for preventive and higher rates for curative applications.
3 Use shorter intervals when conditions are very favorable for disease.
* Products marked with an asterisk are not labeled for home lawn use.
Efficacy Rating
++++ = excellent control when conditions are highly favorable for disease development
+++ = good control when disease pressure is high, excellent control when disease pressure is moderate
++ = good control when disease pressure is moderate, excellent control when disease pressure is low
+ = good control when disease pressure is low
? = not rated due to insufficient data
Resistance Risk
Low = Rotate to different chemical class after 3-4 applications; tank mixing not necessary
Medium = Rotate to different chemical class after 1-2 applications; tank-mixing with low or medium risk product recommended
High = Rotate to different chemical class after EVERY application; tank-mix with low or medium risk product for EVERY application
? = not rated due to insufficient data

Species Data

Rust

Figure 1. Rust.

Rust

Figure 2. Rust.

Rust

Figure 3. Rust.

Rust

Figure 4. Rust.

Rust

Figure 5. Rust.

Rust stand symptoms

Figure 6. Rust stand symptoms.

Rust stand symptoms.

Figure 7. Rust stand symptoms.

Rust stand symptoms.

Figure 8. Rust stand symptoms.

Rust foliar symptoms

Figure 9. Rust foliar symptoms.

Rust foliar symptoms

Figure 10. Rust foliar symptoms.

Rust foliar symptoms

Figure 11. Rust foliar symptoms.

Rust foliar symptoms

Figure 12. Rust foliar symptoms.

Rust foliar symptoms

Figure 13. Rust foliar symptoms.

Rust foliar symptoms

Figure 14. Rust foliar symptoms.

Rust foliar symptoms

Figure 15. Rust foliar symptoms.

Rust foliar symptoms

Figure 16. Rust foliar symptoms.

Rust foliar symptoms

Figure 17. Rust foliar symptoms.

Rust foliar symptoms

Figure 18. Rust foliar symptoms.

Rust foliar symptoms

Figure 19. Rust foliar symptoms.

Rust foliar symptoms

Figure 20. Rust foliar symptoms.

Rust foliar symptoms

Figure 21. Rust foliar symptoms.

Rust foliar symptoms

Figure 22. Rust foliar symptoms.

Rust foliar symptoms

Figure 23. Rust foliar symptoms.

Author:

Extension Coordinator
Entomology and Plant Pathology

Publication date: Nov. 10, 2017

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. Cooperative Extension county center.

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